JPWO2008038670A1 - Fluorescent lamp for flashing, backlight device, and liquid crystal display device - Google Patents

Abstract

The fluorescent lamp (2) of the present invention includes a phosphor layer (23) formed on the inner surface of the glass container (21). The phosphor layer has a 90% emission rise time of 5 milliseconds or less and a phosphor with a 1/10 afterglow time of 5 milliseconds or less (specifically, Sn2 +, Pr3 +, Eu2 +, Eu3 +, Ce3 +). And a phosphor containing an activator selected from the group consisting of Tb3 +. Since this fluorescent lamp can be blinked quickly, the occurrence of an afterimage can be suppressed when used as a backlight of a flashing lighting type liquid crystal display device that blinks a backlight in accordance with driving of the liquid crystal.

Description

  The present invention relates to a fluorescent lamp, a backlight device, and a liquid crystal display device used for blinking lighting.

  Conventionally, the lighting method of the backlight device used for liquid crystal televisions, etc., has been mainly the method of always lighting the lamp (hereinafter referred to as the conventional method), but in recent years, the method of lighting the lamp while turning on and off (hereinafter referred to as the following method). Development of a blinking lighting system) is underway.

  As blinking lighting methods, there are generally known blinking lighting methods that light up in accordance with the on / off timing of a plurality of arranged lamps, and scanning lighting methods that light up while sequentially scrolling by shifting the lamp on / off timing. Yes. Any of these methods has an advantage that motion blur caused when displaying a moving image can be prevented by combining with driving of liquid crystal.

  That is, these blinking lighting systems are attracting attention as means for solving the problems of liquid crystal televisions that are generally said to be weak against moving images. Such a flashing type backlight device is disclosed in International Publication No. 04/053826 pamphlet, Japanese Unexamined Patent Application Publication No. 2004-87489, Japanese Unexamined Patent Application Publication No. 2003-84739, Japanese Unexamined Patent Application Publication No. 2002-6815, and the like. .

  However, in the backlight device using such a blinking lighting method, it is possible to prevent motion blur that occurs when displaying a moving image to some extent, but it is not possible to sufficiently prevent it, and an afterimage remains a big problem It has become.

  As a result of investigations by the inventors with respect to this problem, it has been found that there is also a cause in the response speed of the phosphor used in the fluorescent lamp constituting the backlight device. That is, when the fluorescent lamp used in the conventional method is used in the blinking lighting method, the conclusion is reached that the above problem occurs because the phosphor reacts with delay to the on / off input to the fluorescent lamp.

  As a result of repeated research on the fluorescent substance suitable for this blinking lighting method, it was possible to realize a blinking lighting fluorescent lamp, a backlight device, and a liquid crystal display device in which an afterimage is less likely to remain than before. I came to propose.

  An object of the present invention is to provide a fluorescent lamp for blinking lighting, a backlight device, and a liquid crystal display device in which an afterimage hardly remains.

  In order to achieve the above object, the flashing lighting fluorescent lamp of the present invention has a multi-wavelength phosphor made of a plurality of types of phosphors having a 1/10 afterglow time of 5 msec or less on the inner surface of a glass container. It is characterized by that.

  In the blinking lighting fluorescent lamp of the present invention, the phosphor has a 90% emission rise time of 5 msec or less.

  Furthermore, in the blinking lighting fluorescent lamp of the present invention, the phosphor contains an activator selected from Sn2 +, Pr3 +, Eu2 +, Eu3 +, Ce3 +, and Tb3 +.

  Further, in the blinking lighting fluorescent lamp of the present invention, the phosphor is a multi-wavelength phosphor including red, green, and blue phosphors, and the red phosphor is Sn2 +, Pr3 +, Eu2 +, Eu3 +, and the green phosphor Eu2 +, Ce3 +, Tb3 +, and a blue phosphor contain an activator selected from Eu2 +.

  In addition, the backlight device of the present invention includes a housing, the fluorescent lamp housed in the housing, and a lighting circuit capable of blinking and lighting the fluorescent lamp.

  In addition, a liquid crystal display device of the present invention includes the above backlight device and a liquid crystal panel disposed on the light emitting surface side of the backlight device.

  According to the present invention, it is possible to realize a blinking lighting fluorescent lamp, a backlight device, and a liquid crystal display device in which an afterimage is unlikely to remain.

The figure for demonstrating the backlight apparatus of the 1st Embodiment (embodiment) of this invention. The figure for demonstrating the cross section of the fluorescent lamp shown in FIG. The figure for demonstrating the light emission characteristic of the fluorescent lamp which apply | coated the fluorescent substance of Y203: Eu3 +. The figure for demonstrating the presence or absence of an afterimage when the moving image on a liquid crystal is projected with the fluorescent lamp from which response speed differs. The figure for demonstrating the light emission characteristic when the lamp | ramp of Example (Example) 1 blinks by blinking lighting. The figure for demonstrating the light emission characteristic when the lamp | ramp of Comparative Example (Comparison Example) 1 blinks by blinking lighting. The figure for demonstrating the difference of Example 1 and the comparative example 1. FIG. The figure for demonstrating the response speed of the fluorescent lamp when using various fluorescent substance. The figure for demonstrating the response speed of the fluorescent lamp when combining the fluorescent substance of FIG. The figure for demonstrating the backlight apparatus of the 2nd Embodiment of this invention. The figure for demonstrating the liquid crystal display device of the 3rd Embodiment of this invention. 4A and 4B are diagrams for explaining light emission obtained by the liquid crystal display device of the present invention.

Detailed Description of the Invention

    Hereinafter, a backlight device using a blinking lighting fluorescent lamp according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram for explaining a backlight device according to a first embodiment of the present invention.

  The backlight device BL of the present embodiment is a direct type. The casing of the backlight device BL is composed of a front frame 1a and a back frame 1b. An opening surface is formed in the front frame 1a. The back frame 1b has a bottomed opening shape, and a highly reflective reflecting surface is formed inside thereof.

  Inside the back frame 1b, a plurality of elongated fluorescent lamps 2 are arranged so that their tube axes are substantially parallel to each other. Although a cold cathode fluorescent lamp is used in the present embodiment, a hot cathode fluorescent lamp, an external electrode fluorescent lamp, a flat fluorescent lamp, or the like may be used, and the type, shape, size, etc. are not limited.

  A specific structure of the fluorescent lamp 2 is shown in FIG.

  The main part of the fluorescent lamp 2 is composed of, for example, a glass container 21 made of soft glass, and a mixed gas composed of Ne and Ar and mercury are sealed therein. Electrode mounts 22a and 22b are sealed at both ends of the glass container 21. The electrode mounts 22a and 22b are composed of electrodes 22a1 and 22b1 and bead glasses 22a2 and 22b2.

  A phosphor 23 is formed on the inner surface of the glass container 21. In the present invention, it is desirable to use a phosphor having a high response speed. FIG. 3 is a diagram for explaining the light emission characteristics of a fluorescent lamp coated with a Y203: Eu3 + phosphor. In the figure, the horizontal axis represents time, and the vertical axis represents voltage or current value. The waveform (A) in the figure is an on / off signal that is a voltage waveform for controlling the on / off of the fluorescent lamp, the waveform (B) is the lamp voltage waveform, the waveform (C) is the lamp current waveform, and the waveform (D) is the light emission intensity of the lamp. Is an output voltage waveform obtained by performing photoelectric conversion with a photodiode. These waveforms are measured and displayed by an oscilloscope.

  As can be seen from the figure, the fluorescent lamp 2 responds to the on / off signal waveform (A) in the lamp voltage and lamp current waveforms (B) and (C) without delay, but the reaction of the light emission waveform (D) of the lamp is There is a tendency to be late. This is a result of the response speed of the phosphor. Therefore, it is most desirable to use a phosphor whose response speed is the same as that of the on / off signal (A), but such a phosphor is difficult to realize.

  Therefore, the inventor investigated the response speed of various phosphors, and 1/10 afterglow time (when the maximum brightness is A, the time from when the lamp brightness changes from A to 0.1 A) is approximately A three-wavelength fluorescent lamp with a duration of 1 msec to 10 msec was prepared. Then, a moving image on a liquid crystal was projected with the fluorescent lamp, and a test was conducted on 10 subjects to see if there was an afterimage in the moving image.

  The results are shown in FIG. As can be seen from FIG. 4, it was found that if the 1/10 afterglow time was 5 msec or less, it was difficult to be seen as an afterimage by human eyes, and if it was 3 msec or less, it was hardly recognized as an afterimage. Incidentally, the Y203: Eu3 + phosphor shown in FIG. 3 has both a 90% rise time and a 1/10 afterglow time of about 2.5 msec, so the response speed in flashing lighting is fast and suitable as the phosphor of the present invention. Yes. In most phosphors, it was found that the rise of light emission and the fall of light emission have a correlation. For example, the phosphor of FIG. 3 has a 1/10 afterglow time of 2.5 msec, while a 90% light emission rise time (time until the lamp brightness is changed from O to 0.9 A) is also about 3 msec. That is, since the 1/10 afterglow time and the 90% light emission rise time are almost the same result, it can be said that a phosphor with a fast emission fall is a phosphor with a fast emission rise.

  In FIG. 1, a diffusion plate 3 is disposed on the opening side of the back frame 1b. As the diffusing plate 3, it is desirable to use a light diffusing plate having a transmittance of 50% to 85% so that unevenness in light emission can be reduced and efficiency is not lowered excessively.

  An optical sheet 4 is disposed on the diffusion plate 3. As the optical sheet 4, one sheet or a plurality of sheets such as a diffusion sheet and a prism sheet can be used according to the purpose.

  A lighting circuit 5 is disposed on the back side of the back frame 1b. The lighting circuit 5 may be any circuit as long as the fluorescent lamp 2 can be lit in a blinking manner, and a typical example is a PWM (Pulse Width Modulation) circuit. In the case of this PWM circuit, it is desirable to light the lamp with a frequency of 50 to 300 Hz and a duty ratio of 10 to 70%. In this case, as a matter of course, it is desirable to set the frequency and the duty ratio so that the lamp off period becomes longer than the 1/10 afterglow time from the viewpoint of suppressing the afterimage.

  The specification of the Example and comparative example of the backlight apparatus of this invention is shown below.

(Example 1)
Backlight device BL; size = 32 inches (about 760mm × about 440mm),
Fluorescent lamp 2; cold cathode fluorescent lamp, inner diameter = 2.Omm, outer diameter = 3.Omm, lamp current = 6.OmA, number of lamps used = 16, lamp pitch = 23.8mm, fluorescent lamp 2 and diffusion plate 3 Distance = 14mm,
Phosphor 23; Y203: Eu3 + (R), Y2Si5: Tb3 + (G), BaMg2Al10O17: Eu2 + (B),
Diffuser 3; transmittance = 60%,
Optical sheet 4; diffusion sheet, prism sheet,
Lighting circuit 5: PWM circuit, frequency = 50Hz, duty ratio = 50%.

(Comparative Example 1)
Phosphor 23; Y203: Eu3 + (R), LaPO4: Ce3 +, Tb3 + (G), BaMg2Al10Ol7: Eu2 + (B),
The configuration other than the phosphor 23 has the same specifications as in Example 1.

  FIG. 5 is a diagram for explaining the light emission characteristics when the lamp of Example 1 and FIG. 6 are flashed by blinking lighting of the lamp of Comparative Example 1. In these figures, the horizontal axis represents time, and the vertical axis represents voltage or current value. The waveform (A) in the figure is an on / off signal that is a voltage waveform for controlling the on / off of the fluorescent lamp, the waveform (B) is the lamp voltage waveform, the waveform (C) is the lamp current waveform, and the waveform (D) is the light emission intensity of the lamp. Is an output voltage waveform obtained by performing photoelectric conversion with a photodiode.

  Comparing the light emission waveforms of FIG. 5 and FIG. 6, it can be seen that the response speed of the lamp is faster in Example 1 than in Comparative Example 1. Specifically, the 1/10 afterglow time of Example 1 is about 3 msec and Comparative Example 1 is about 7 msec, and Example 1 is turned off earlier. Also, with respect to the 90% light emission rise time, Example 1 is less than 3 msec, while Comparative Example 1 is less than 8 msec.

  In addition, when each lamp was mounted on a liquid crystal display device and a movie was taken, Example 1 hardly remained as an afterimage, but in Comparative Example 1, it was obvious that the afterimage remained and the movie looked blurred. . Further, in order to further eliminate the afterimage, the brightness of the two was compared when the liquid crystal was closed at the lamp turn-off timing, that is, the lamp brightness was obtained only during the lamp turn-on period. As a result, when the duty ratio was 100%, the luminance of both of them with respect to the luminous flux of the lamp was about 95% in Example 1 and about 70% in Comparative Example 1. That is, the liquid crystal display device using Example 1 was clearly felt brighter.

  The reason for such a result is presumed as follows.

  The difference between Example 1 and Comparative Example 1 is only that a green phosphor having a different response speed with respect to the on / off signal is used as shown in FIG. However, as is apparent from FIGS. 5 and 6, when a three-wavelength phosphor is used, there is a large difference between the rise and afterglow of the lamp. From this, in the case of blinking lighting using a fluorescent lamp 2 coated with a three-wavelength phosphor, if the response speed is slow even in one of R (red), G (green), B (blue) phosphor, It was estimated that the response speed of the fluorescent lamp would be slow.

  Therefore, when a three-wavelength phosphor combining various phosphors was formed on a lamp and tested, it was confirmed that the phosphor with the slowest response speed in all of them determined the response speed of the three-wavelength phosphor. It was done. Therefore, in the three-wavelength fluorescent lamp for blinking lighting, it is necessary to use a combination of phosphors having a high response speed in all RGB. In addition, in 4-wavelength phosphors mixed with phosphors such as red, green, blue, and crimson, or multi-wavelength phosphors mixed with more phosphors, only when the response speed of all the phosphors is fast, It is possible to realize a fluorescent lamp having a fast light emission response speed.

Here, further research by the inventors discovered the fact that the response speed of the phosphor is mainly related to the activator of the phosphor. That is, the composition of the phosphor is expressed as Y203: Eu3 +, and Y203 is generally called a matrix and Eu3 + is called an activator, but as can be seen from FIG. 8, the response speed of the phosphor is the activator. I found that it almost depends on. Therefore, when a test was conducted by paying attention to the phosphor activator, the phosphor composed of an activator selected from Sn2 +, Pr3 +, Eu2 +, Eu3 +, Ce3 +, Tb3 + is 1/10 of 5 msec or less. It was found that the afterglow time was easy to realize. However, since Eu3 + and Tb3 + activators have a response speed of several msec, there are phosphors whose 1/10 afterglow time exceeds 5 msec depending on the combination with the base material. Therefore, in these cases, only a phosphor having a 1/10 afterglow time of 5 msec or less is suitable for blinking lighting. On the other hand, Sn2 +, Pr3 +, Eu2 +, and Ce3 + activators have 90% emission rise time and 1/10 afterglow time of about 0.1 msec, and the phosphor responds almost without delay to the on / off signal. It can be said that it is particularly suitable for flashing lighting applications. Incidentally, when a plurality of activators are used, the characteristics of the activator having the slowest response speed tend to be obtained as the response speed of the phosphor. For example, LaPO4: Ce3 +, Tb3 +, which is the green phosphor of Comparative Example 1, contains Ce3 + with a fast response speed, but has a response speed of Tb3 + with a slower response speed. That is, in the case of a plurality of activations, if an activator having a slow response speed is included in one of them, it is not suitable as a phosphor used for blinking lighting.

  In addition, since the characteristic of a fluorescent substance changes with the kind and valence, there exist an activator which can be used for every desired luminescent color, and an activator which cannot be used. Sn2 +, Pr3 +, Eu2 +, Eu3 +, Ce3 +, Tb3 + activators are Sn2 +, Pr3 +, Eu2 +, Eu3 + are red phosphors, Eu2 +, Ce3 + are green phosphors, Tb3 +, Eu2 + are blue phosphors can do.

  Next, as shown in FIG. 9, three-wavelength fluorescent lamps using various RGB phosphors were created and the response speed was tested. As a result, the 90% emission rise time was about 3 msec for Examples 2, 3, and 5, 1 msec or less for Example 4, and 10 msec or more for Comparative Examples 2 and 3. Further, the 1/10 afterglow time was about 3 msec in Examples 2, 3, and 5, 1 msec or less in Example 4, about 6 msec in Comparative Example 2, and 10 msec or more in Comparative Example 3. From the above, it has been confirmed that any combination of phosphors having a high response speed can be applied to a flashing and lighting backlight device regardless of the combination.

  Further, the fluorescent lamp of the present invention is also effective when performing dimming by the PWM method. That is, dimming is performed mainly for the purpose of adjusting the contrast, but as a result, it is possible to obtain an effect that an afterimage hardly remains.

  Therefore, in the first embodiment, an afterimage is formed by using a fluorescent lamp in which an RGB phosphor 23 having a 1/10 afterglow time of 5 msec or less is applied to the inner surface of the glass container 21 and blinking. A backlight device that does not easily remain can be provided. Also, in most cases, such phosphors have a 90% emission rise time of 5 msec or less, so when the liquid crystal display device is configured by synchronizing the lamp and liquid crystal on / off, the luminance loss of the lamp is small, High brightness can be realized.

  Specifically, the red phosphor is composed of Sn2 +, Pr3 +, Eu2 +, Eu3 +, the green phosphor is composed of Eu2 +, Ce3 +, Tb3 +, the blue phosphor is composed of a three-wavelength phosphor including an activator selected from Eu2 +. Thus, the above effect can be reproduced.

  In the above embodiment, the blinking lighting method is used as the lighting method of the backlight device, but the present invention can also be effectively applied to a scanning lighting type backlight device.

  FIG. 10 is a diagram for explaining a scanning lighting type backlight device. In this backlight device, each of the 12 lamps is divided into two lamps to form six lamp groups, and each lamp group is input with an on / off signal shifted by 1/6 at a time to perform scanning lighting. ing. The on / off signal has a frequency = 60 Hz, a duty ratio = 50%, and is generated by the PWM method. This scanning lighting method is different from the blinking lighting method in that one or more of the lamp groups are always on in the lighting state. realizable.

(Second embodiment)
FIG. 11 is a diagram for explaining an embodiment of a liquid crystal display device using the fluorescent lamp of the present invention.

  In the liquid crystal display device, a housing is constituted by a front case FC and a back case BC. A liquid crystal panel LCP is disposed on the opening surface of the front case FC. The back case BC has a shape of a bottomed opening, and a backlight device BL is disposed therein.

  In the case of a liquid crystal display device, it is possible to combine the blinking lighting of the backlight device BL and the operation of opening and closing the liquid crystal panel LCP. FIG. 12 is a diagram for explaining light emission characteristics when the lamp of the backlight device BL is lit in a blinking manner. In the figure, the horizontal axis represents time, and the vertical axis represents voltage or current value. Further, the waveform (A) in the figure is an on / off signal that is a voltage waveform for controlling on / off of the fluorescent lamp, the waveform (B) is a lamp voltage waveform, the waveform (C) is a lamp current waveform, and the waveform (D) is a lamp waveform. It is an output voltage waveform obtained by photoelectrically converting the emission intensity with a photodiode. Further, waveform (E) is a signal for opening and closing the liquid crystal forming the liquid crystal panel LCP, waveform (F) is a light emission waveform obtained by the liquid crystal panel LCP, and waveform (G) is a light emission not obtained by the liquid crystal panel LCP. It is a waveform.

  As shown in Fig. 12, the afterglow of the lamp can be cut by closing the liquid crystal panel LCP at the same time that the OFF signal is input to the backlight device BL, so the combination of both causes almost complete motion blur. It is possible to prevent. However, since the cut light cannot be used as the light of the liquid crystal, the luminance is reduced accordingly. For example, in Comparative Example 1, the luminance is reduced by about 30%. In that respect, in the backlight device using the fluorescent lamp of the present invention, since the response speed of the lamp is fast, the light that is cut is reduced, and high luminance can be achieved.

  Therefore, in the second embodiment, it is possible to realize a liquid crystal display device with high luminance and little afterglow even in flashing lighting.

Claims (12)

  A glass container in which a discharge medium is enclosed; a discharge electrode provided at an end of the glass container; and multi-wavelength fluorescence composed of a plurality of types of phosphors formed on the inner surface of the glass container. Fluorescent lamp for blinking lighting, characterized in that the body has a 1/10 afterglow time of 5 msec or less.   2. The blinking lighting fluorescent lamp according to claim 1, wherein the phosphor has a 90% emission rise time of 5 msec or less.   2. The flashing lighting fluorescent lamp according to claim 1, wherein the phosphor includes an activator selected from Sn2 +, Pr3 +, Eu2 +, Eu3 +, Ce3 +, and Tb3 +.   3. The flashing fluorescent lamp according to claim 2, wherein the phosphor includes an activator selected from Sn2 +, Pr3 +, Eu2 +, Eu3 +, Ce3 +, and Tb3 +.   The phosphor is a multi-wavelength phosphor including red, green, and blue phosphors, the red phosphor is selected from Sn2 +, Pr3 +, Eu2 +, Eu3 +, the green phosphor is selected from Eu2 +, Ce3 +, Tb3 +, and the blue phosphor is selected from Eu2 +. 2. The flashing fluorescent lamp according to claim 1, further comprising an activator that has been activated.   The phosphor is a multi-wavelength phosphor including red, green, and blue phosphors, the red phosphor is selected from Sn2 +, Pr3 +, Eu2 +, Eu3 +, the green phosphor is selected from Eu2 +, Ce3 +, Tb3 +, and the blue phosphor is selected from Eu2 +. 3. The flashing lighting fluorescent lamp according to claim 2, further comprising an activator prepared.   The phosphor is a multi-wavelength phosphor including red, green, and blue phosphors, the red phosphor is Sn2 +, Pr3 +, Eu2 +, the green phosphor is Eu2 +, Ce3 +, and the blue phosphor is an activation selected from Eu2 + 2. The blinking lighting fluorescent lamp according to claim 1, further comprising an agent.   The phosphor is a multi-wavelength phosphor including red, green, and blue phosphors, the red phosphor is Sn2 +, Pr3 +, Eu2 +, the green phosphor is Eu2 +, Ce3 +, and the blue phosphor is an activation selected from Eu2 + 3. The fluorescent lamp for blinking lighting according to claim 2, further comprising an agent.   6. A backlight device comprising: a housing; the fluorescent lamp according to claim 5 housed in the housing; and a lighting circuit capable of blinking the fluorescent lamp.   7. A backlight device comprising: a housing; the fluorescent lamp according to claim 6 housed in the housing; and a lighting circuit capable of blinking the fluorescent lamp. The backlight device according to claim 9,
A liquid crystal display device comprising: a liquid crystal panel disposed on a light emitting surface side of the backlight device. The backlight device according to claim 10,
A liquid crystal display device comprising: a liquid crystal panel disposed on a light emitting surface side of the backlight device.

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